A report on Igneous rock

Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)
Natural columns of igneous rock separated from each other by columnar joints, in Madeira
Formation of igneous rock
Basic types of intrusions:
Extrusive igneous rock is made from lava released by volcanoes
Sample of basalt (an extrusive igneous rock), found in Massachusetts
Close-up of granite (an intrusive igneous rock) exposed in Chennai, India
Gabbro specimen showing phaneritic texture, from Rock Creek Canyon, eastern Sierra Nevada, California
Basic classification scheme for igneous rocks based on their mineral composition. If the approximate volume fractions of minerals in the rock are known, the rock name and silica content can be read off the diagram. This is not an exact method, because the classification of igneous rocks also depends on other components, yet in most cases it is a good first guess.
Total alkali versus silica classification scheme (TAS) as proposed in Le Maitre's 2002 Igneous Rocks – A classification and glossary of terms Blue area is roughly where alkaline rocks plot; yellow area is where subalkaline rocks plot.
AFM ternary diagram showing the relative proportions of Na2O + K2O (A for Alkali earth metals), FeO + Fe2O3 (F), and MgO (M) with arrows showing the path of chemical variation in tholeiitic and calc-alkaline series magmas
Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition because different minerals crystallize from the melt. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms.
Kanaga volcano in the Aleutian Islands with a 1906 lava flow in the foreground
A "skylight" hole, about {{cvt|6|m}} across, in a solidified lava crust reveals molten lava below (flowing towards the top right) in an eruption of Kīlauea in Hawaii
Devils Tower, an eroded laccolith in the Black Hills of Wyoming
A cascade of molten lava flowing into Aloi Crater during the 1969-1971 Mauna Ulu eruption of Kilauea volcano
Columnar jointing in the Alcantara Gorge, Sicily
A laccolith of granite (light-coloured) that was intruded into older sedimentary rocks (dark-coloured) at Cuernos del Paine, Torres del Paine National Park, Chile
An igneous intrusion cut by a pegmatite dike, which in turn is cut by a dolerite dike

One of the three main rock types, the others being sedimentary and metamorphic.

- Igneous rock
Volcanic eruptions of lava are major sources of igneous rocks. (Mayon volcano in the Philippines, erupting in 2009)

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Basalt

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QAPF diagram with basalt/andesite field highlighted in yellow. Basalt is distinguished from andesite by SiO2 < 52%.
Basalt is field B in the TAS classification.
Vesicular basalt at Sunset Crater, Arizona. US quarter (24mm) for scale.
Columnar basalt flows in Yellowstone National Park, USA
Columnar basalt at Szent György Hill, Hungary
Large masses must cool slowly to form a polygonal joint pattern, as here at the Giant's Causeway in Northern Ireland
Columns of basalt near Bazaltove, Ukraine
Photomicrograph of a thin section of basalt from Bazaltove, Ukraine
An active basalt lava flow
The Giant's Causeway in Northern Ireland
Columnar jointed basalt in Turkey
Columnar basalt at Cape Stolbchaty, Russia
Pillow basalts on the Pacific seafloor
Paraná Traps, Brazil
Lunar olivine basalt collected by Apollo 15 astronauts
Kaolinized basalt near Hungen, Vogelsberg, Germany
Metamorphosed basalt from an Archean greenstone belt in Michigan, US. The minerals that gave the original basalt its black colour have been metamorphosed into green minerals.
The Code of Hammurabi was engraved on a 2.25m tall basalt stele in around 1750 BC.

Basalt is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon.

Granite containing potassium feldspar, plagioclase feldspar, quartz, and biotite and/or amphibole

Granite

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Granite containing potassium feldspar, plagioclase feldspar, quartz, and biotite and/or amphibole
Thin section of granite
QAPF diagram with granite field highlighted in yellow
Mineral assemblage of igneous rocks
The Cheesewring, a granite tor in England
A granite peak at Huangshan, China
Pink granite at Hiltaba, South Australia (part of the Hiltaba Suite)
Granite with quartz veins at Gros la Tête cliff, Aride Island, Seychelles
Grus sand and granitoid it derived from
Granite dimension stone quarry in Taivassalo, Finland
Cleopatra's Needle, London
Granites (cut and polished surfaces)
The granite castle of Aulanko in Hämeenlinna, Finland
Curling stones
Granite was used for setts on the St. Louis riverfront and for the piers of the Eads Bridge (background)
The granite peaks of the Cordillera Paine in the Chilean Patagonia
alt=Half Dome, Yosemeite National Park|Half Dome, Yosemite National Park, is actually a granite arête and is a popular rock climbing destination
Rixö red granite quarry in Lysekil, Sweden
Granite in Auyuittuq National Park on Baffin Island, Canada
Granite in Paarl, South Africa

Granite is a coarse-grained (phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase.

Lava flow on Hawaii. Lava is the extrusive equivalent of magma.

Magma

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Lava flow on Hawaii. Lava is the extrusive equivalent of magma.
Phase diagram for the diopside-anorthite system
Schematic diagrams showing the principles behind fractional crystallisation in a magma. While cooling, the magma evolves in composition because different minerals crystallize from the melt. 1: olivine crystallizes; 2: olivine and pyroxene crystallize; 3: pyroxene and plagioclase crystallize; 4: plagioclase crystallizes. At the bottom of the magma reservoir, a cumulate rock forms.
A single silica tetrahedron
Two silica tetrahedra joined by a bridging oxygen ion (tinted pink)

Magma is the molten or semi-molten natural material from which all igneous rocks are formed.

Crystals of serandite, natrolite, analcime, and aegirine from Mont Saint-Hilaire, Quebec, Canada

Mineral

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In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.

In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.

Crystals of serandite, natrolite, analcime, and aegirine from Mont Saint-Hilaire, Quebec, Canada
Schist is a metamorphic rock characterized by an abundance of platy minerals. In this example, the rock has prominent sillimanite porphyroblasts as large as 3 cm.
Hübnerite, the manganese-rich end-member of the wolframite series, with minor quartz in the background
When minerals react, the products will sometimes assume the shape of the reagent; the product mineral is termed a pseudomorph of (or after) the reagent. Illustrated here is a pseudomorph of kaolinite after orthoclase. Here, the pseudomorph preserved the Carlsbad twinning common in orthoclase.
Topaz has a characteristic orthorhombic elongated crystal shape.
Contact twins, as seen in spinel
Diamond is the hardest natural material, and has a Mohs hardness of 10.
Pyrite has a metallic lustre.
Perfect basal cleavage as seen in biotite (black), and good cleavage seen in the matrix (pink orthoclase).
Galena, PbS, is a mineral with a high specific gravity.
Carnotite (yellow) is a radioactive uranium-bearing mineral.
Aegirine, an iron-sodium clinopyroxene, is part of the inosilicate subclass.
Natrolite is a mineral series in the zeolite group; this sample has a very prominent acicular crystal habit.
Muscovite, a mineral species in the mica group, within the phyllosilicate subclass
Asbestiform tremolite, part of the amphibole group in the inosilicate subclass
An example of elbaite, a species of tourmaline, with distinctive colour banding.
Epidote often has a distinctive pistachio-green colour.
Black andradite, an end-member of the orthosilicate garnet group.
Native gold. Rare specimen of stout crystals growing off of a central stalk, size 3.7 x 1.1 x 0.4 cm, from Venezuela.
Red cinnabar (HgS), a mercury ore, on dolomite.
Sphalerite crystal partially encased in calcite from the Devonian Milwaukee Formation of Wisconsin
Pink cubic halite (NaCl; halide class) crystals on a nahcolite matrix (NaHCO3; a carbonate, and mineral form of sodium bicarbonate, used as baking soda).
Gypsum desert rose

Orthoclase feldspar (KAlSi3O8) is a mineral commonly found in granite, a plutonic igneous rock.

Gabbro specimen

Gabbro

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Gabbro specimen
Photomicrograph of a thin section of gabbro
Mineral assemblage of igneous rocks
QAPF diagram with the gabbroid/dioritoid fields highlighted in yellow. Gabbroids are distinguished from dioritoids by an anorthosite content of greater than 50% of their plagioclase.
QAPF diagram with the gabbro field highlighted in yellow. Gabbro is distinguished from diorite by an anorthosite content of greater than 50% of its plagioclase and from anorthite by a mafic mineral content greater than 10%.
A gabbro landscape – the main ridge of the Cuillin, Isle of Skye, Scotland
Cizlakite sample
Zuma Rock, Nigeria, a massive, nearly uniform, intrusion of gabbro and granodiorite.

Gabbro is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface.

QAPF diagram for the classification of plutonic rocks

Intrusive rock

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Formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.

Formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.

QAPF diagram for the classification of plutonic rocks
Devils Tower, an igneous intrusion exposed when the surrounding softer rock eroded away
An intrusion (pink Notch Peak monzonite) inter-fingers (partly as a dike) with highly metamorphosed black-and-white-striped host rock (Cambrian carbonate rocks) near Notch Peak, House Range, Utah
Diagram showing various types of igneous intrusion
Dark dikes intruded into the country rock, Baranof Island, Alaska, United States

Intrusion is one of the two ways igneous rock can form.

Quartzite, a type of metamorphic rock

Metamorphic rock

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Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism.

Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism.

Quartzite, a type of metamorphic rock
A metamorphic rock, deformed during the Variscan orogeny, at Vall de Cardós, Lérida, Spain
Metamorphic rock containing staurolite and almandine garnet
A mylonite (through a petrographic microscope)
Folded foliation in a metamorphic rock from near Geirangerfjord, Norway
Mississippian marble in Big Cottonwood Canyon, Wasatch Mountains, Utah.
A contact metamorphic rock made of interlayered calcite and serpentine from the Precambrian of Canada. Once thought to be a pseudofossil called Eozoön canadense. Scale in mm.
Basalt hand sample showing fine texture
Amphibolite formed by metamorphosis of basalt

The protolith may be an igneous, sedimentary, or existing metamorphic rock.

Middle Triassic marginal marine sequence of siltstones (reddish layers at the cliff base) and limestones (brown rocks above), Virgin Formation, southwestern Utah, U.S.

Sedimentary rock

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Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation.

Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation.

Middle Triassic marginal marine sequence of siltstones (reddish layers at the cliff base) and limestones (brown rocks above), Virgin Formation, southwestern Utah, U.S.
Uluru (Ayers Rock) is a large sandstone formation in Northern Territory, Australia.
Claystone deposited in Glacial Lake Missoula, Montana, United States. Note the very fine and flat bedding, common for deposits coming from lake beds further away from the source of sediment.
Sedimentary rock with sandstone in Malta
Lower Antelope Canyon was carved out of the surrounding sandstone by both mechanical weathering and chemical weathering. Wind, sand, and water from flash flooding are the primary weathering agents.
Outcrop of Ordovician oil shale (kukersite), northern Estonia
Fossils of Nerinea marine gastropods of Late Cretaceous (Cenomanian) age, in limestone in Lebanon
Cross-bedding and scour in a fine sandstone; the Logan Formation (Mississippian) of Jackson County, Ohio
Pressure solution at work in a clastic rock. While material dissolves at places where grains are in contact, that material may recrystallize from the solution and act as cement in open pore spaces. As a result, there is a net flow of material from areas under high stress to those under low stress, producing a sedimentary rock that is harder and more compact. Loose sand can become sandstone in this way.
A piece of a banded iron formation, a type of rock that consists of alternating layers with iron(III) oxide (red) and iron(II) oxide (grey). BIFs were mostly formed during the Precambrian, when the atmosphere was not yet rich in oxygen. Moodies Group, Barberton Greenstone Belt, South Africa
Diagram showing well-sorted (left) and poorly sorted (right) grains
Diagram showing the rounding and sphericity of grains
Global collage of sand samples. There is one square centimeter of sand on every sample photo. Sand samples row by row from left to right: 1. Glass sand from Kauai, Hawaii 2. Dune sand from the Gobi Desert 3. Quartz sand with green glauconite from Estonia 4. Volcanic sand with reddish weathered basalt from Maui, Hawaii 5. Biogenic coral sand from Molokai, Hawaii 6. Coral pink sand dunes from Utah 7. Volcanic glass sand from California 8. Garnet sand from Emerald Creek, Idaho 9. Olivine sand from Papakolea, Hawaii.
Fossil-rich layers in a sedimentary rock, Año Nuevo State Reserve, California
Burrows in a turbidite, made by crustaceans, San Vincente Formation (early Eocene) of the Ainsa Basin, southern foreland of the Pyrenees
Cross-bedding in a fluviatile sandstone, Middle Old Red Sandstone (Devonian) on Bressay, Shetland Islands
Flute casts, a type of sole marking on the base of a vertical layer of Triassic sandstone in Spain
Ripple marks formed by a current in a sandstone that was later tilted (Haßberge, Bavaria)
Halite crystal mold in dolomite, Paadla Formation (Silurian), Saaremaa, Estonia
Chert concretions in chalk, Middle Lefkara Formation (upper Paleocene to middle Eocene), Cyprus
Common types of depositional environments
The swirls of tan, green, blue, and white are sediment in the shallow waters of the Gulf of Mexico off the Yucatan Peninsula. The blue-green cloud in this image roughly matches the extent of the shallow continental shelf west of the peninsula. This is a perfect example of a shallow marine depositional environment.
Shifting sedimentary facies in the case of transgression (above) and regression of the sea (below)
Plate tectonics diagram showing convergence of an oceanic plate and a continental plate. Note the back-arc basin, forearc basin, and oceanic basin.
Cyclic alternation of competent and less competent beds in the Blue Lias at Lyme Regis, southern England
The Permian through Jurassic stratigraphy of the Colorado Plateau area of southeastern Utah that makes up much of the famous prominent rock formations in protected areas such as Capitol Reef National Park and Canyonlands National Park. From top to bottom: Rounded tan domes of the Navajo Sandstone, layered red Kayenta Formation, cliff-forming, vertically jointed, red Wingate Sandstone, slope-forming, purplish Chinle Formation, layered, lighter-red Moenkopi Formation, and white, layered Cutler Formation sandstone. Picture from Glen Canyon National Recreation Area, Utah.
Distribution of detritus
Sedimentary rocks on Mars, investigated by NASA's Curiosity Mars rover
Steeply dipping sedimentary rock strata along the Chalous Road in northern Iran
Stratified remains of Puʻu Mahana cinder cone.
A regressive facies shown on a stratigraphic column

Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks.

Feldspar crystal (18×21×8.5 cm) from Jequitinhonha valley, Minas Gerais, southeastern Brazil

Feldspar

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Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium, or barium.

Feldspars are a group of rock-forming aluminium tectosilicate minerals, containing sodium, calcium, potassium, or barium.

Feldspar crystal (18×21×8.5 cm) from Jequitinhonha valley, Minas Gerais, southeastern Brazil
Compositional phase diagram of the different minerals that constitute the feldspar solid solution.
Diagram showing part of a crankshaft chain of feldspar
Feldspar crystal structure viewed along the c axis
Feldspar crystal structure viewed along the a axis
Feldspar crystal structure viewed along the b axis
Specimen of rare plumbian (lead-rich) feldspar
Perched on crystallized, white feldspar is an upright 4 cm aquamarine crystal
Feldspar and moonstone, from Sonora, Mexico
Schorl crystal on a cluster of euhedral feldspar crystals
First X-ray view of Martian soil—feldspar, pyroxenes, olivine revealed (Curiosity rover at "Rocknest", October 17, 2012).<ref name="NASA-20121030">{{cite web |last=Brown |first=Dwayne |title=NASA Rover's First Soil Studies Help Fingerprint Martian Minerals |url=http://www.nasa.gov/home/hqnews/2012/oct/HQ_12-383_Curiosity_CheMin.html |date=October 30, 2012 |publisher=NASA |access-date=October 31, 2012}}</ref>
Lunar ferrous anorthosite #60025 (plagioclase feldspar). Collected by Apollo 16 from the Lunar Highlands near Descartes Crater. This sample is currently on display at the National Museum of Natural History in Washington, D.C.

Feldspars crystallize from magma as both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock.

Diorite

Diorite

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Diorite
Orbicular diorite from Corsica (corsite)
QAPF diagram with dioritoid fields highlighted in yellow and diorite in red
Mineral assemblage of igneous rocks
Hornblende diorite from the Henry Mountains, Utah, US
Naqada II jar with lug handles; c. 3500–3050 BC; height: 13 cm; Los Angeles County Museum of Art (US)
Statue of Gudea I, dedicated to the god Ningishzida; 2120 BC (the Neo-Sumerian period); height: 46 cm, width: 33 cm, depth: 22.5 cm; Louvre
Weight dedicated by King Shulgi with a crescent moon on it; 2094-2047 BC; weight: 248 g; Louvre
Assyrian head of a bearded god wearing a cap with horns dedicated by Puzur-Eshtar of Mari; middle Bronze Age; height: 37 cm; Vorderasiatisches Museum Berlin (Berlin, Germany)
Head of a cow goddess (Hathor or Mehetweret); 1390-1352 BC; height: 53.6 cm, width: 28 cm, depth: 33 cm; Metropolitan Museum of Art (New York City)
Statue of Amun; 1336-1327 BC; height: 220 cm, width: 44, length: 78 cm; Louvre
Block statue of the god's father Pameniuwedja, son of Nesmin and Nestefnut; 4th century BC; height: 34.6 cm, width: 14.5 cm, depth: 19.1 cm; Metropolitan Museum of Art
Vase with gilt-bronze ornaments; circa 1780; 61 × 40.6 cm; Metropolitan Museum of Art
Palazzo delle Poste di Napoli, Gino Franzi, 1936. The masterpiece of modernism, made of marble and diorite.

Diorite is an intrusive igneous rock formed by the slow cooling underground of magma (molten rock) that has a moderate content of silica and a relatively low content of alkali metals.